Push-pull amplifier



PUSH-PULL AMPLIFIER Filed Aug. 50, 1930 INVENTOR POPKO RElNDER DYKSTERHUIS BY H'gAW/M/ ATTORN EY Patented Oct. 24, 1933 PATENT since PUSH-PULL AMPLIFIER Popko Reinder Dyksterhuis, EindhovenjNetherlands, assignor to Radio Corporation of America, a corporation of Delaware Application August so, 1930, Serial No. 478,831,

and in the Netherlands September 2, 1929 9 Claims. (01. 179-171) V v ment is different. By slightly shifting the slid- The present invention relates to amplifiers, and more particularly to improvements in, or relating to, circuit arrangements for push-pull amplifiers.

This invention has reference to push-pull amplifiers, and has for its main object to provide a circuit arrangement that permits in a simple manner the controlling of the intensity, and of adjusting the balance.

According to this invention, for the purpose, the cathodes and the negative terminal of the source of anode current have interconnected between them a resistance consisting of-one or more parts and traversed by the anode direct current, a variable point of the said resistance being connected to the cathode, and at least one of the grids being connected to a second variable point. I v

The novel features which I believe to be characteristic of my invention are'set forthin particularity in the appended'claims, the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection With-the drawing in which I have indicated diagrammatically one circuit arrangement wherebymy invention maybe carried into effect.

Referring to the single figure, 1 and 2 designate triodes connected in push-pull in the "usual manner. The grids 15 are supplied from transformers 3 and 4, which, in reality, are'notnec essarily separated, as shown in the figure, but which may form a single push-pull transformer as Well known to those skilled in the prior art. Thesecondary windings 3', 4' of transformers 3 and 4 are connected to the cathodes 14 through condensers 16 and 17. The cathodes 14 are, in addition, connected through resistances 8 and 5 to the negative terminal of the source of anode current.

A sliding contact 9 permits the short-circuiting of part of the resistance 8. It is thus possible to give the grid bias any desired value. The secondary windings of the transformers 3 and 4 are connected through resistances, or inductances,.13 and 12 respectively to the points 7 and 6 of the resistance 5. In the figure, the point 7 is to be considered variable, whereas the point 6 is to be assumed stationary.

The function of the latter arrangement is to permit compensation for any disparity in the two triodes, since if no particular means are taken it often occurs that the direct current of the two triodes of a push-pull circuit arrangeing contact 7 the direct current in one triode can be equalized in a simple manner with that in the other, an exact push-pull connection being thus ensured. It is possible to test the uniformity of the direct current inthe two triodes for example by including a milliamrneter in each of the two anode circuits.

The negative terminal of the anode current source and the sliding contact 'I have interconnected between them a high resistance 11. The latter ensures that if at a' given moment the sliding contact 7 does not make contact with the resistance 5, nevertheless the grid of one of the triodes is not insulated, which might give rise to wideundesired potential variations.

It is, of course, obvious'that the point 6 may be variable. In this case it is necessary to interconnect between this point and the negative terminal of the anode current source a high resistance having the same function as the resistance '11. The resistances, or inductances, 12, 13 and the condensers 16 and 17 are particularly important if the anode current is supplied from a high tension unit. In this case the said elements act as filters, and annul any alternatingvoltages that may still occur and give rise It is, of course, obvious that the resistances 5 and 8 are not necessarily separated, but may be combined to form asingle unit. The anodes of the tubes 1, 2 are connected, in any Well known manner to a utilization circuit.

While I have indicated and described one arrangement for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organization shown and described, but that many modifications in the circuit arrangements, may be made without departing from the scope of 'my invention as set forth in the appended claims.

What I claim is:

1. The combination of current supply means, a push-pull amplifier, a connection'between the positive terminal of said means andthe anodes of the amplifier, a second connection between the cathodes of the latter and the negative termi nal of said means, said second connection including a bias resistor path for the grids of the amplifier, a connection between each grid of the amplifier and the resistor path, at least one of the grid connections being adjustable to secure exact push-pull operation of the amplifier, and an independent adjustable connection between the said cathodes and said path to provide means for regulating the bias of said grids.

2. The combination of current supply means, a push-pull amplifier, a connection between the positive terminal of said means and the anodesof the amplifier, a second connection between the cathodes of the latter and the negative terminal of said means, said second connection including a bias resistor for the grids of the amplifier, a connection between each grid of the amplifier and the resistor, at least one of the grid connections being adjustable to secure exact pushpull operation or" the amplifier, and a resistor connected between the said negative terminal and said adjustable grid connection to maintain said adjustably connected grid biased at all times.

3. The combination of current supply means, a push-pull amplifier, a connection between the positive terminal of said means and the anodes of the amplifier, a second connection between the cathodes of the latter and the negative terminal of said means, said second connection including a bias resistor for the grids of the amplifier, a connection between each grid of the amplifier and the resistor, at least one'ofthe grid connections being adjustable to secure exact pushpull operation of the amplifier, a variable resistor included in series withcthe bias resistor in said second connection to control the magnitude of bias applied to both grids of the amplifier, and a reactive path connected between each of the said-grid connections and said cathodes to suppress hum due to pulsations in said supply means. 7

4. The combination of current supply means, a push-pull amplifier, a connection between the positive terminal of said means and the anodes of the amplifier, a second connection between the cathodes of the latter and the negative terminal of said means, said second connection including a bias resistor for the grids of the amplifier, a connection between each grid of the amplifier and the resistor, at least one of the grid connections being adjustable to secure exact push-pull operation of the amplifier, and a condenser connected between the cathodes of the amplifier and a point on each of said grid bias connections.

5. The combination of current supply means, a push-pull amplifier, a connection between the positive terminal of said'means and the anodes of the amplifier, a second connection between the cathodes of the latter and the negative terminal of said means, said second connection including a bias resistor for the grids of the amplifier, a connection between each grid of the amplifier and theresistor, at least one of the grid connections being adjustable to secure exact push-pull operation of the amplifier, additional means associated with the second connection for controlling the biasing potential of said grids, and means common to the grid and cathode circuits of the amplifier for suppressing hum due to pulsations in said supply means.

6. The combination of current supply means, a push-pull amplifier, a connection between the positive terminal of said means and the an es of the amplifier, a second connection between the cathodes of the latter and the negative terminal of said means, said second connection including a bias resistor for the grids of the amplifier, a connection between each grid of the amplifier and the resistor, at least one of the grid connections being adjustable to secure exact push-pull operation of the amplifier, a resistor connected between one end of the bias resistor and the adjustable grid connection and the other grid connection to the bias resistor being fixed.

7., The combination of current supply means, a push-pull amplifier, a connection between the positiveterminalof said means and the anodes of the amplifier, a second connection between the cathodes of the latter and the negative terminal of said means, said second connection including a bias resistor for the grids of the amplifier, a connection between each grid of theamplifier and the resistor, at least one of the grid connections being adjustable to secure exact push pull operation of the amplifier, a fixed resistor connected between the bias resistor and the adjustable grid connection to insure a, bias at all times on theyadjustably connected grid, a variable resistor included in series with the bias resistor in said second connection to control the magnitude of bias applied to bothv grids of the amplifier, and a reactive path connected between each of the said grid connections and said cathodes to suppress hum due to pulsations in said supply means.

8. The combination of current supply means,

a push-pullamplifier, a connection between the positive terminal of said means and the anodes of the amplifier, a second connectionbetween the cathodes of the latter-and the negativeterminal of said means, said second connection including a bias resistor for-the grids of the amplifier, a connection between each gridoi the amplifier and the resistor, at least one of the grid connections being adjustable to secure exact push-pull operation of the amplifier, a variable resistor included in series with the bias resistor in said second connection to control the magnitude of bias applied to both grids of the amplifier, and a reactive path including a cas pacity connected between each of the said grid connections-and said cathodes to suppress hum due to pulsations-in said supply means.

9. The combination of current supply means, a push-pull amplifier, a connection between the positive terminal of said means and the anodes of the amplifier, a second connection between the cathodes of the latter and' the negative terminal of said means, said second connection ineluding a bias resistor for the grids of the amplifier, a connection between each grid of the amplifier and the resistor, at least one or" the grid connections being adjustable to secure exact push-pull operation of the amplifiena fixed renections and said cathodes to suppresshum due,

to pulsations in said supply means.

POPKO REINDER DYKSTERHUIS. 

